Commercial riding lawn mowers of the type used on golf courses, athletic fields and the like, are relatively large machines which often utilize cutting reels as opposed to rotary blades. Typically on such mowers two or three cutting reels are provided across the front of the mower. Additionally, one or more cutting reels are positioned in trailing relationship behind the gaps between the front cutting reels. The cutting reels make direct contact with the grass when cutting, following the contour and undulations of the terrain as the mower moves over the ground. The Toro Company, which is the assignee hereof, manufactures and sells several examples of such mowers.
Although the present invention relates to turf maintenance vehicles usable in a large variety of situations (including but not limited to cutting grass in parks, athletic fields, golf courses, etc.), the maintenance of golf courses will be utilized herein for the purposes of illustration. Now continuing with the golf course example, it will be immediately appreciated that cutting grass on a golf course is a recurring and time consuming task. Further, the particular tee or fairway is typically taken out of service while the cutting is occurring. Accordingly, it is desirable to drive the mower as fast as possible while maintaining the desired cutting height and quality of cut, since the ground speed of the mower while cutting is directly related to the time necessary to cut the particular tee or fairway. However, in such settings the potential ground speed depends upon the ability of the cutting reels to maintain the desired quality of cut. Those skilled in the art will appreciate that the potential ground speed is also affected by variations in the terrain, the experience of the operator, and the turf conditions. Still other considerations include the type of grass, the moisture on the grass and/or the moisture content of the grass, and the desired cutting height of the grass.
In determining whether the cutting reels are maintaining the desired quality of cut, two broad categories may be considered. The first category is whether the cut is "clean." A clean cut may be defined as the absence of straggler or uncut blades of grass after the reel passes over the turf. A cleaner cut results in a healthier turf due to reduced tendancy to thatch build-up. In the golf course example, a better playing surface results from a cleaner cut since ball roll is improved. The second category is the "clip." Those skilled in the art will recognize that a reel mower cuts turf in a manner which creates slight undulations in the height of the turf. The difference in linear distance between adjacent peaks of the undulations are commonly referred to as the clip. While reduction of the clip maximizes the appearance of turf, the required high reel speed at higher ground speeds creates an unclean cut--due to a knocking over of the blades of grass rather than cutting, among other problems. Thus, the complete elimination of the clip is at odds with the foregoing goal of achieving a high ground speed. Accordingly, a certain amount of clip must be tolerated, and, in fact, it has been found that certain clips can be aesthetically pleasing. The difference in height between the troughs and peaks will be referred to herein as the restitution height, and it will be appreciated that such height is interelated to the clip--and in fact aids in the clip length to be apparent to an observer. A more detailed discussion of clip is presented further below.
In the past, the cutting reel speed has been fixed to the speed of the wheels in a mechanical manner. For example, The Toro Company, assignee of the present application, has for many years manufactured and sold a turf maintenance device under the model designation Spartan.RTM.. In this device the reel cutting units are driven by mechanical gears which in turn are driven by wheels which engage the ground. The device employed a fixed ratio such that the faster the ground speed, the faster the reel speed. One problem presented by this system is that it does not take into account the height of cut, which must be considered when determining the optimized clip. A second problem with such a mechanical reel drive system is that to optimize the clip the reel speed is not a constant linear function of ground speed. Since the operators of the equipment may either not understand these requirements or may forget, a less than optimum clip often results.
Other systems, such as the mower identified by the model designation Reelmaster.RTM. 223-D, also manufactured by The Toro Company, provide a variable reel speed control. This control allows an operator to manually adjust the opening of the hydraulic fluid passageway in the manifold of the reel drive system in order to vary the reel speed. Accordingly, this system provides a mechanically preset adjustment which should be based on ground speed, number of cutting blades on the reel, and the intended height of cut ("HOC"). However, the system is not dynamic in the sense that it is not self correcting (i.e., there is no feedback control taking into account the actual ground speed, and no corrections are made without operator intervention). The drawback of such a system is that it is wholly dependent upon the operator presetting the system correctly and to continue to operate the mower at the intended speed during the mowing process. Not only is such a system not predictable due to the human element introduced, but it also introduces additional time required to mow the various areas if adjustments are required.
Accordingly, there arises a need for a turf maintenance vehicle controller which preferably includes an automated reel speed system to optimize clip, as well as providing additional features.